In this ShEEP grant, we request funds to purchase an UltraFocus dual x-ray absorptiometry (DXA) instrument from Faxitron for installation in the phenotype core of Musculoskeletal Disease Center of VA Loma Linda Healthcare System (VALLHCS). The UltraFocus DXA system is a self-contained x-ray unit and workstation with a 10 X 15 cm CMOS detector coupled with the energy range from 10-100 kV that makes this instrument ideal for imaging a broad range of samples as well as for true DXA analysis. The microfocus tube with up to a 6X geometric magnification provides up to 8 m image resolution. The system has been validated to automatically calculate bone mineral density, bone mineral content, and lean and fat body mass percentages in both the whole body as well as in regions of interest. This new instrument will be used by a number of investigators at the VALLHCS to perform musculoskeletal phenotype work. Studies proposed in various funded studies involve knockout and transgenic mouse strains which will require routine phenotyping by a DXA system. The software that comes with the system allows automated and precise quantitation of bone mineral density and bone mineral content. The system also allows for obtaining high quality images for data documentation and publication. A number of VA, DOD and NIH funded investigators at this VA Medical Center including Drs. Mohan, Rundle, Qin, Lau, Edderkaoui and Xing require this equipment to perform studies related to their funded grant applications. This system will replace a PIXImus DXA that was purchased about 15 years ago and has been non-functional for more than 6 months. The PIXImus instrument was purchased from the Lunar Corporation that stopped manufacturing or servicing this instrument several years ago. We were unable to fix the existing PIXImus as the parts or service is no longer available for this instrument. The requested instrument is needed for successful completion of funded studies that are relevant to the pathogenesis and treatment of osteoporosis and osteoarthritis, diseases that are target areas of the VA research mission.